Summary In the tropical canopy tree, Dryobalanops aro-

sunlit conditions but are subjected to self-shading within the crown as they age. In contrast, lower-canopy leaves (LL) are exposed to uniform dim light conditions throughout their life span. By comparing leaf morphology and physiology of UL and LL, variations in leaf characteristics were related to leaf age and self-shading. Mass-based chlorophyll (chl) concentra-tion and the chlorophyll/nitrogen (chl/N) ratio were lower and the chl a/b ratio was higher in UL than in LL. In UL, the chl/N ratio gradually increased and the chl a/b ratio gradually de-creased with leaf aging, whereas these ratios remained un-changed with leaf age in LL. The effective quantum yield of photosystem II (PSII) (∆F/Fm′) at a given irradiance remained unchanged with leaf age in LL, whereas ∆F/Fm ′ changed with leaf age in UL. These data indicate N reallocation within the leaves from carbon fixation components to light harvesting components and a dynamic regulation of photochemical proc-esses of PSII in response to increased self-shading of UL. Despite the difference in light environment with leaf age be-tween UL and LL, maximum photosynthetic rates and nitro-gen-use efficiency decreased with leaf aging in both UL and LL. Constancy in the chl/N ratio with leaf age in LL indicated that the decrease in photosynthetic capacity was caused by effects other than shading, such as leaf aging. We conclude that N reallocation and acclimation of PSII to self-shading occurred even in mature leaves, whereas the change in photosynthetic capacity with leaf age was more conservative